Identity and topographic localization of immunocompetent cells and alteration of surface marker on ocular resident cells in rodents with experimental autoimmune uveoretinitis by active immunization or adoptive transfer were analyzed by immunohistochemical studies. The lymphocyte population at the inflammatory sites was found to change markedly during the course of disease. In the early stage, T-helper/inducers are the predominant cells in the eye. A relative increase of T- suppressor/cytotoxic cells in the late stage were observed. Expression of major histocompatibility complex class II antigens on ocular resident cells such as RPE, retinal endothelium, keratocytes, fibroblast and ciliary epithelium was observed in different models of EAU. This antigen expression may play a certain role in the pathogenesis of EAU. Both infiltrating and alteration of class II antigens cell subpopulation can be modulated by cyclosporine and dexamethosone treatment.